Modern production processes in wood industry have a very high production speed. This brings about high requirements for the reliability and effectiveness of quality control during the processes. It is well known that the traditional ways to monitor product defects during e.g. plywood production result in high reject rates of the final product due to the delay between the actual production and availability of quality testing results thereof. For glued or impregnated products the main sources of defects are related to the binder and its interaction with the substrate. Already small differences between different glue batches (e.g. viscosity or molecular weight distribution) or in the properties of the substrate (e.g. moisture content or density) will significantly change the adsorption and absorption behavior of the binder on and into the substrate. Consequently, gluing phase is the most challenging part in plywood production process. Problems in gluing can usually be seen only after hot pressing when it is already too late.
The inventors of the present invention have recognized a need for better systems to monitor the quality of the glued substrates on which binder composition has been applied. The current invention relates to a new method for producing a fiber based product, comprising a way to monitor the uniformity of the applied binder composition.